Extreme Science is a website that has a lot of simplistic definitions and explanations for many of the common themes and topics of the Earth Sciences and Biology.
NASA home page has loads of science and technology based information, that is put into a graphical and interactive format. It covers a wide range of topics beyond space related topics.
This sight is an interactive resource for teachers of all content areas in Highschool. It has flash games and visual aids on core subject content, that can help create a more interactive and visual class. Pbs also has blogs for parents and teachers to connect on many of the content areas.
The US national website for everything education related including news. blogs, best practices, and information about becoming accredited and getting grants.